The present invention relates to a method in operating a cavern for gas.
There is a need for intermediate storage of gas, such as natural gas, which is distributed via pipelines from sources of natural gas, e.g. with a view to managing the distribution during peak use of pipelines.
Intermediate storage of natural gas under pressure is already known. Deep-seated (about 1000-2000 m below ground level), unlined aquifers and salt formations have been used as storage. Lined caverns (LRC, Lined Rock Cavern) at a little depth (100-150 m below ground level) have also been disclosed, see e.g. FI-69503, where the natural gas is stored at a high pressure (150 bar) and at a temperature of xc2x10xc2x0 C. to xc2x16xc2x0 C., that is in the form of gas.
The lining of caverns has been described as consisting of a sandwich construction, see e.g. FI-69503 and xe2x80x9cDemo Plant for Lined Gas Stores at Grxc3xa4ngesberg. Deeper Analysis of the Test Resultsxe2x80x9d, TRITA-AMI Report 3004 (1995), the common denominator of these documents being a gas-tight layer (steel, plastic) on the inside and a support layer (concrete) on the outside, in which latter drainage pipes are embedded, among other things, for the drainage of water. The thickness of the support layer is selected in consideration of, for instance, the desired temperature insulation capacity.
If a lined cavern is to be filled with natural gas from a pipeline, the natural gas is compressed to the nominal working pressure of the cavern, the quantity of natural gas storable in the cavern at the maximum permissible pressure being limited by a temperature corresponding to this pressure after the compression.
It is desirable to be able to increase the quantity of stored gas, such as natural gas, at a certain pressure (maximum permissible pressure) in a cavern.
The object of the invention is to satisfy these requirements, which is achieved by one embodiment of the invention described herein.
Another object of the invention is to reduce the risks of damage to the lining due to repeated freezing and low temperatures, and this object is achieved by according to a further embodiment of the invention described herein. As a result, it is also possible to save costs by reducing the thickness of the lining of newly constructed caverns.